1. Field of the Invention
The present invention relates to a communication device, a communication system and a communication method for carrying out communications by using a prescribed control program on a network such as the Echonet.
2. Description of the Related Art
In recent years, there has been active development of the so called information home electronics in which a communication function is provided in home appliances such as refrigerator, washer, etc., AV home electronics, information devices such as PC, mobile devices such as portable telephone, etc., and various functions utilizing the digital technology have been proposed for each device.
One of the applications of the information home electronics is the use of a home network. The home network is a network technology developed for a network inside the home, for interconnecting various information home electronics mentioned above and carrying out communications.
As this type of the home network technology, the Internet technology has been attracting much attentions recently. For example, many applications that are attractive to the home network users such as those of music distribution, home page viewing, e-mails, etc., have been developed and the number of users is steadily increasing.
On the other hand, one exemplary application of the home network is a facility related network, or the use of the home network for the home automation. It is possible to connect air conditioners, lights, home appliances, etc., to the home network and carry out applications such as device state monitoring, remote controlling, etc.
In Japan, the Echonet is expected to be the de facto standard for this type of the facility related network. The Echonet defines commands, protocols, objects, API, etc. for controlling facility related devices (home appliances, etc.) on various physical media such as electric power lines, twisted pair lines, etc. Further details of the Echonet can be found in documents disclosed at the URL “http://www.echonet.gr.jp”, for example. The Echonet is standardized by a consortium founded mainly by several Japanese electronics companies, which has already issued the specification version 1, and the commercial application is about to start.
The Echonet has its own address system, so that there is a need for a mechanism to use the address system of the Echonet on the address system of the Internet. The Echonet address is a logical address, so that there is a need to carrying out a procedure for determining the Echonet address at a time of turning on the power of the device, for example.
However, the determination of the Echonet address is a part of the initialization procedure which have to be carried out by all nodes, so that it is necessary to account for a problem such as “if a plurality of nodes that are wishing to use the same address exist simultaneously at a time of the initialization, how this situation should be handled”, and in the case of determining a specific server at a time different from a time of determining the address, a problem such as “if a plurality of nodes that are trying to becomes a specific server exist simultaneously, how this situation should be handled”. Otherwise, the problem of the conflict will arise, and in the worst case, there is a possibility for an occurrence of a situation in which the overlap of addresses or servers occurs, or else the initialization processing is repeated indefinitely.
As for the determination of the address to be used for communications, there has been a proposition disclosed in Japanese patent application laid open No. 2000-183941, for example.